1. Field of the Invention
The present invention relates to optical apparatuses capable of zooming. More particularly, the present invention relates to an optical apparatus for image taking and an optical apparatus for observation, for example, a digital still camera, a video camera, or an interchangeable lens.
2. Description of the Related Art
A typical lens apparatus including a plurality of moving lens units adopts a mechanical interlocking mechanism using a cam ring, and a driving portion (actuator) for each of the moving lens units.
Computer zooming is known in which each driving portion (actuator) performs zooming and focusing.
To reduce the cost by sharing the driving portion, there has been proposed a mechanism in a lens apparatus for driving two moving lens units by one actuator.
For example, in a mechanism disclosed in Japanese Patent Laid-Open No. 64-84233, a zoom lens unit and a focus lens unit are driven by a single driving portion while switching an interlocking movement mechanism, such as a plunger, so as to perform zooming and focusing in order.
Japanese Laid-Open No. 04-24606 discloses a mechanism in which a bifocal zoom lens unit and a focus lens unit are driven by a single driving portion so as to perform switching between two focal points and focusing in order.
A lens apparatus provided with an optical system in which zooming is performed by two zoom lens units in different areas in accordance with the zoom position will be considered.
In this case, to drive the two zoom lens units by mechanical interlocking using a cam ring, it is necessary to adopt a cam driving mechanism that uses a gear reduction device or the lie and that generates high torque to drive the cam ring.
Because of this complicated cam driving mechanism, operating noise, such as tapping noise of gears that constitute the cam driving mechanism, increases. Hence, the cam driving mechanism is not suitable for movie taking that also records sound.
However, even when the two zoom lens units are applied to the above-described two mechanisms that perform zooming and focusing in order, it is difficult to realize continuous zooming.